Birds have feathers, beaks without teeth, and wings that evolved from forelimbs. They have lightweight skeletons, sharp eyesight, and a four-chambered heart. Their respiratory system includes small lungs and air sacs that allow for unidirectional airflow. Birds circulate blood efficiently through their hearts and have adaptations like larger hearts for flight. Their nervous systems control body functions and sense the environment through highly developed brains and sense organs. Birds digest food through a complete digestive system including a gizzard instead of teeth. They excrete nitrogenous wastes like uric acid through a cloaca and reproduce through internal fertilization and egg-laying.

2. Animal Diversity: Vertebrates
by
Maryam Riasat
BIRDS

3. Birds

4. Birds
 Birds includes pigeons, owls and flamingos
 Birds are bipedal and clawed vertebrates
 Body is covered by feathers
 Birds body is divisible into head, neck, trunk
and tail
 Small head is placed on a fairly long movable
neck
• A beak with no teeth
• Have sharp eyesight
• A lightweight but strong skeleton
• Production of hard-shelled eggs
• Forelimbs are modified into wings
• Hind limbs are strong and are useful to walk
• High metabolism
• A four chambered heart
• They have well developed flight muscles

5. Respiration
 The birds respiratory system is
different from that of other
vertebrates
 They have relatively small lungs
plus nine air sacs that play an
important role in respiration
 The air sacs permit a
unidirectional flow of air through
the lungs
 The birds respiratory
system delivers oxygen from the
air to the tissues and also removes
carbon dioxide

6. Circulation
 Birds have four chambered hearts made of the right atrium,
right ventricle, left atrium and left ventricle
 The division helps for efficient flow of oxygenated and
deoxygenated blood
 Birds also have specific adaptations for flight, including a
larger heart relative to body weight and a faster heart rate

7. Nervous system
 Highly developed nervous system,
includes brain and sense organs
 The nervous system integrates and
controls the various functions of the
body, while the sensory organs detect
the various stimuli in the bird's
environment
 The avian nervous system can be
divided into the central nervous system
(CNS) which comprises the brain and
spinal cord
 The peripheral nervous system (PNS)
which includes the cranial and spinal
nerves and ganglia

8. Digestive System
 Birds have complete digestive
system
 The digestive order is as
follows: bill, mouth, tongue,
pharynx, esophagus, crop,
proventriculus, gizzard, small
intestine, caeca, rectum, cloaca.
 Alimentary canal contains gizzard
for crushing the food due to
absence of teeth.

9. Excretory system
• The excretory system consists of the
two kidneys, each with a ureter that
carries the urine produced by the
kidneys to the cloaca where it leaves
the body
• Unlike mammals, do not have
separate exits for urine and feces.
Both waste products are eliminated
simultaneously through the cloaca
• Birds excrete nitrogenous wastes in
the form uric acid or guanine, which
reduces water loss

10. Reproduction
 Birds reproduce by internal fertilization,
during which the egg is fertilized inside the
female
 All birds reproduce by laying eggs
 Eggs are produced inside the female and then
deposited in a nest
 Fertilized ovum then forms the nucleus of the
egg and the formation of the yolk, whites and
shell